Ch. 2 Matter & Change

Properties of Matter Matter: anything that has mass and takes up space Mass: amount of matter the object contains Physical Property: characteristic that can be observed or measured without changing the sample’s composition Extensive properties: depends on the quantity of matter (length, mass, volume) Intensive properties: independent of the quantity present (melting & boiling point, density)

Properties of Matter Chemical Property: ability of a substance to combine with or change into one or more substances *can only be determined by changing the substance Ex. Iron combines with oxygen to form iron oxide (rust) Each substance has a unique set of chemical and physical properties

Changes in Matter Physical Change: alter a substance without changing its composition Changes state – all transition like melting, freezing, boiling, condensing Can be classified as reversible or irreversible Chemical Change: a process that involves one or more substances changing into a new substance Known as a chemical reaction New chemical: different composition and properties

Evidence of a Chemical Change Color change Energy changes – gets cold or hot Odor change Precipitate (solid formed from a mixture of solution) Gas produced – bubbles Irreversible process New properties

Solid: definite shape and volume States of Matter Solid: definite shape and volume Particles are very tightly packed – incompressible Difficult to squeeze a solid into a smaller volume Expands slightly when heated Most are crystalline – regular, repeating pattern Other are amorphous – no internal pattern (plastic, glass, gel)

Liquid: definite volume, no definite shape States of Matter Liquid: definite volume, no definite shape Particles can move past one another – fluidity Takes the shape of the container Expands slightly when heated Incompressible

Gas: no definite volume or shape States of Matter Gas: no definite volume or shape Flows Expands to fill the volume of the container Particles are very far apart – compressible Vapor: used to describe the gaseous state of a substance that is normally a solid or liquid at room temperature (water vapor, mercury vapor)

Mixtures of Matter 1. Substance: 2. Mixture: Substance: matter with uniform – definite composition Cannot be altered by physical methods Every sample of a given substance has identical intensive properties because every sample has the same composition Example: copper 2. Mixture: Combination of two or more substances in which each retains its individual chemical properties Heterogeneous and homogeneous

Pure Substances Elements: Substance that is composed of only one type of atom Building blocks of matter Cannot be further separated by chemical or physical methods 91 naturally occurring elements Scientists developed the rest of the elements Uranium is the largest natural element

Elements Origins of name: Periodic Table: Greek, Latin, or German names based on properties Location or Scientist of discovery Commemoration of famous scientist Periodic Table: Originally developed by Dmitri Mendeleev in 1869 Altered into current version Pattern of similar properties repeat

Pure Substances Compounds: Substance that is composed of two or more elements that are combined chemically Properties of a compound are generally very different from the elements that make it Chemical Formulas: Formulas show the symbols on the ratio of the elements in the compound Subscripts: tell the number of each element in the compound Ex. C12H22O11

Common Compounds Water H2O Glucose C6H12O6 Sucrose C12H22O11 Carbon Dioxide CO2 Methane CH4 Ammonia NH3

Heterogeneous Mixture: Mixtures Heterogeneous Mixture: Not uniform in composition Individual substances remain distinct Each sample will have parts in different amounts Ex. Chicken noodle soup, sand in water

Mixtures Homogeneous Mixture: Constant, uniform composition Each sample will have the parts in the same ratio Ex. Tea, air, saltwater, antifreeze Solution: another name for homogeneous mixture Alloy: a solid-solid solution, usually two metals Ex. Steel and brass

Separating Mixtures Filtration: Mixtures are a physical combination Separation techniques use differences in physical properties Filtration: Used for heterogeneous solid-liquid mixtures Porous filter paper traps the solid as the liquids pass through Ex. A colander separates pasta from the water in which it cooked Distillation: Used for homogeneous liquid-liquid mixtures Based on differences in boiling point Uses condenser Ex. Alcohol and water

Separating Mixtures Crystallization: Chromatography: Pure solid forms from a solution Example: rock candy Chromatography: Separates components based on relative attraction to two separate phases (mobile and stationary)

Law of Conservation of Mass: Mass is neither created or destroyed in a chemical reaction - it is conserved Law of Definite Proportions: Regardless of the amount, a compound is always composed of the same elements in the same proportion by mass Law of Multiple Proportions: The same elements can form different compounds by combining in different ratios CO2 – carbon dioxide CO – carbon monoxide